1. Technical Field
The present invention relates to an atomic oscillator and a manufacturing method, and more particularly to an atomic oscillator in which a light-emitting element, a gas cell and a light-receiving element are vertically stacked, and a manufacturing method of the same.
2. Related Art
In recent years, as the development of a digital network, such as a communication network or a broadcast network, proceeds, a highly accurate and highly stable oscillator is indispensable as a clock source used for generation of a clock signal of a transmission apparatus or a reference frequency of a broadcast station. As such an oscillator, a rubidium atomic oscillator having a highly accurate and stable oscillation frequency is often used. Besides, in recent years, a request for miniaturization of an atomic oscillator is increased, and the necessity to miniaturize the overall size including a gas cell is compelled. At the same time, a manufacturing method in which the manufacturing cost can be reduced is requested in order to reduce the unit cost.
U.S. Pat. No. 6,900,702 B2 (Patent Document 1) discloses a structure of an atomic oscillator in which light emitted from a light source is refracted by a prism and passes through a gas cell, and is further refracted by a prism and is received by a light-receiving element.
In the related-art atomic oscillator, as one means for improving the production efficiency, a manufacturing method is adopted in which plural gas cells are integrally formed, and are later diced into single chips. However, the structure is such that the light-emitting element, the gas cell, and the light-receiving element are laterally arranged on the substrate and a certain interval is ensured between the respective members, and further, the plural mirrors to refract the light are required. Thus, it can not be necessarily said that the miniaturization is realized in the whole unit.
Besides, since the related art disclosed in Patent Document 1 uses the expensive parts such as the prism, there is a problem that the unit cost is high.